@kunchenguid: my new video is up! this is a popular request I received from my last video about agentic engineering workflow full wal…

TL;DR

Starting from a fresh Mac, build a reproducible, declarative agentic engineering development environment step by step using Nix Darwin, Home Manager, WezTerm, Starship, and more.

Why a Reproducible Configuration Matters

Manually setting up a new machine (or quickly recovering after an AI agent crashes your system) is both time‑consuming and error‑prone. My solution is Nix – a declarative, reproducible configuration system originally designed for NixOS, but now fully usable on macOS via the Determinate Nix installer.

Step 1: Install Nix

1. Open a terminal and run the Determinate Nix install command (see the video description).
2. Type yes and wait for the installation to finish.
3. Run the refresh command shown in the prompt to activate the new environment.

Step 2: Create the Config Repo & Nix Darwin

Initialize the repository

mkdir files && cd files
git init
ln -s "$(pwd)" ~/files   # Create a fixed symlink so scripts can refer to it easily

Configure Nix Darwin

flake.nix template (remember to replace the username and version):

{
  description = "macOS configuration";
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/23.11";  # Pin a stable version
    nix-darwin.url = "github:LnL7/nix-darwin/23.11";
  };
  outputs = { self, nix-darwin, nixpkgs }: {
    darwinConfigurations.mac = nix-darwin.lib.darwinSystem {
      modules = [ ./configuration.nix ];
    };
  };
}

Basic configuration.nix:

{ config, pkgs, ... }: {
  nix.enable = false;  # Managed by Determinate Nix
  nixpkgs.config.allowUnfree = true;
  system.stateVersion = 6;
  networking.hostName = "mac";  # Example
  users.users."your-username".home = "/Users/your-username";  # Replace
  # System preferences, Homebrew, Home Manager modules will be added here later
}

Apply the configuration

git add -A && git commit -m "initial nix-darwin config"
nix run nix-darwin -- switch --flake .

Create a quick rebuild script rebuild.sh:

#!/bin/bash
nix run nix-darwin -- switch --flake .

chmod +x rebuild.sh

Step 3: Configure macOS System Preferences

Add system settings to configuration.nix (example):

system.defaults = {
  NSGlobalDomain.AppleInterfaceStyle = "Dark";
  NSGlobalDomain.KeyRepeat = 2;       # Fast key repeat
  NSGlobalDomain.InitialKeyRepeat = 15; # Short delay
  dock.autohide = true;
  dock.orientation = "bottom";
  finder.AppleShowAllExtensions = true;
  finder.FXPreferredViewStyle = "Nlsv";  # List view
  desktop.ViewOptions = { ShowDesktopIcons = false; };
  trackpad.Clicking = true;  # Tap to click
};

Run ./rebuild.sh – the settings take effect immediately.

Step 4: Manage Homebrew with Nix

To keep everything fully reproducible, install Homebrew through Nix. Add the input and module to flake.nix:

inputs = {
  # ... existing ...
  nix-homebrew.url = "github:zhaofengli/nix-homebrew";
  homebrew-bundle = { url = "github:homebrew/homebrew-bundle"; flake = false; };
  homebrew-core = { url = "github:homebrew/homebrew-core"; flake = false; };
  homebrew-cask = { url = "github:homebrew/homebrew-cask"; flake = false; };
};
outputs = {
  # ... existing ...
  nix-homebrew.lib, homebrew-bundle, homebrew-core, homebrew-cask, ...
}: {
  darwinConfigurations.mac = nix-darwin.lib.darwinSystem {
    modules = [
      ./configuration.nix
      nix-homebrew.darwinModules.nix-homebrew
      {
        nix-homebrew = {
          enable = true;
          enableRosetta = true;  # Required on Apple Silicon
          user = "your-username";
        };
        homebrew = {
          enable = true;
          cleanup = "zap";  # Remove packages not in Nix config
          casks = [
            "wezterm"  # My terminal of choice
            # Add other casks here
          ];
        };
      }
    ];
  };
};

Run ./rebuild.sh – Homebrew and WezTerm are installed automatically. Verify with brew --version.

Step 5: Home Manager – Manage the User Directory

Home Manager handles user‑level configuration (dotfiles, packages, environment variables). Add to flake.nix:

inputs = {
  # ... existing ...
  home-manager.url = "github:nix-community/home-manager";
  home-manager.inputs.nixpkgs.follows = "nixpkgs";
};
outputs = {
  # ... existing ...
  home-manager, ...
}: {
  darwinConfigurations.mac = nix-darwin.lib.darwinSystem {
    modules = [
      # ... existing ...
      home-manager.darwinModules.home-manager
      {
        home-manager.useGlobalPkgs = true;
        home-manager.useUserPackages = true;
        home-manager.users."your-username" = import ./home.nix;
      }
    ];
  };
};

Create home.nix (initial content):

{ config, pkgs, ... }: {
  home.username = "your-username";
  home.homeDirectory = "/Users/your-username";
  home.stateVersion = "23.11";

  # Create a symlink to the dotfiles repo
  home.file.".config/wezterm".source = ./config/wezterm;

  # User‑level packages
  home.packages = with pkgs; [
    hack-font                     # Hack Nerd Font
    # Other user‑level packages
  ];

  # Environment variables
  home.sessionVariables = {
    EDITOR = "nvim";
  };
}

Create the config/wezterm directory – we’ll fill it with configuration later.

Step 6: Shell Enhancements (Zsh + Starship)

Autosuggestions & Syntax Highlighting

Add to home.nix:

programs.zsh = {
  enable = true;
  enableAutosuggestions = true;
  enableSyntaxHighlighting = true;
  initExtra = ''
    # Ctrl+F accepts autosuggestion
    bindkey '^f' autosuggest-accept
  '';
  shellAliases = {
    ll = "ls -la";
    gs = "git status";
    ga = "git add";
    gc = "git commit";
  };
};

Starship Prompt

Continue adding to home.nix:

programs.starship = {
  enable = true;
  settings = {
    add_newline = false;
    # More customisation options – see Starship docs
  };
};

Run ./rebuild.sh – the new terminal session picks up the changes automatically.

Step 7: WezTerm – The Ultimate Terminal

WezTerm is a high‑performance terminal written in Rust, with cross‑platform Lua configuration. Create ~/.config/wezterm/wezterm.lua:

local wezterm = require 'wezterm'
return {
  -- Colour scheme
  color_scheme = "Rosé Pine Moon",
  -- Font
  font = wezterm.font("Hack Nerd Font", { size = 15 }),
  -- Transparency & blur
  window_background_opacity = 0.85,
  macos_window_background_blur = 20,
  -- Hide tab bar when only one tab is open
  hide_tab_bar_if_only_one_tab = true,
  -- Frameless window
  window_decorations = "RESIZE",
}

Save the file – WezTerm hot‑reloads automatically, and the effect is visible immediately.

Step 8: Neovim – The Main Editor

Create the initial config directory and file:

mkdir -p ~/.config/nvim
touch ~/.config/nvim/init.lua

Then edit init.lua with Neovim and gradually add plugins and settings (later this configuration can be managed through Home Manager to make it reproducible).

Source: YouTube Video by @kunchenguid (https://www.youtube.com/watch?v=5N-okeDdIuI)